;(function(win, lib) {
    var doc = win.document;
    var docEl = doc.documentElement;
    var metaEl = doc.querySelector('meta[name="viewport"]');
    var flexibleEl = doc.querySelector('meta[name="flexible"]');
    var dpr = 0;
    var scale = 0;
    var tid;
    var flexible = lib.flexible || (lib.flexible = {});
    var userAgent = navigator.userAgent.toLowerCase();
    var isIPhone = !!userAgent.match(/\(i[^;]+;( u;)? cpu.+mac os x/);
    var isAndroid = userAgent.indexOf('android') > -1 || userAgent.indexOf('adr') > -1;
    var isTv = userAgent.indexOf("android") >= 0 && userAgent.indexOf("tv") >= 0

    var width = window.screen.width;
    var height = window.screen.height;
    var resolution = width * height;

    if (isAndroid && !isTv && (resolution >= 3840 * 2160 || width >= 1550)) {
        isTv = true
    }

    document.documentElement.style.setProperty('--zoom', 1)
    document.documentElement.style.zoom = 1
    
    if (metaEl) {
        // console.warn('将根据已有的meta标签来设置缩放比例');
        var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/);
        if (match) {
            scale = parseFloat(match[1]);
            dpr = parseInt(1 / scale);
        }
    } else if (flexibleEl) {
        var content = flexibleEl.getAttribute('content');
        if (content) {
            var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
            var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
            if (initialDpr) {
                dpr = parseFloat(initialDpr[1]);
                scale = parseFloat((1 / dpr).toFixed(2));    
            }
            if (maximumDpr) {
                dpr = parseFloat(maximumDpr[1]);
                scale = parseFloat((1 / dpr).toFixed(2));    
            }
        }
    }

    if (!dpr && !scale) {
        var devicePixelRatio = win.devicePixelRatio;
        if (isIPhone) {
            // iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
            if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {                
                dpr = 3;
            } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)){
                dpr = 2;
            } else {
                dpr = 1;
            }
        } else if (isAndroid && !isTv) {
            // 其他设备下，仍旧使用1倍的方案
            dpr = 1;
        } else {
            dpr = window.devicePixelRatio
            zoom = `${1 / window.devicePixelRatio}`
            document.documentElement.style.setProperty('--zoom', zoom)
            document.documentElement.style.zoom = zoom
        }
        scale = 1 / dpr;
    }
    
    if ((isAndroid && !isTv) || isIPhone) {
        docEl.setAttribute('data-dpr', dpr);
        if (!metaEl) {
            metaEl = doc.createElement('meta');
            metaEl.setAttribute('name', 'viewport');
            metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
            if (docEl.firstElementChild) {
                docEl.firstElementChild.appendChild(metaEl);
            } else {
                var wrap = doc.createElement('div');
                wrap.appendChild(metaEl);
                doc.write(wrap.innerHTML);
            }
        }
    }

    function refreshRem(){
        
        if ((!isAndroid && !isIPhone) || isTv) {
            dpr = window.devicePixelRatio
            zoom = `${1 / window.devicePixelRatio}`
            document.documentElement.style.setProperty('--zoom', zoom)
            document.documentElement.style.zoom = zoom
        } else {
            var width = docEl.getBoundingClientRect().width;
            // if (width / dpr > 540) {
            //     width = 540 * dpr;
            // }
            var rem = width / 10;
            docEl.style.fontSize = rem + 'px';
            flexible.rem = win.rem = rem;
            metaEl && metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no');
        }
    }

    win.addEventListener('resize', function() {
        clearTimeout(tid);
        tid = setTimeout(refreshRem, 30);
    }, false);
    win.addEventListener('pageshow', function(e) {
        if (e.persisted) {
            clearTimeout(tid);
            tid = setTimeout(refreshRem, 30);
        }
    }, false);

    if (doc.readyState === 'complete') {
        doc.body.style.fontSize = 12 + 'px';
    } else {
        doc.addEventListener('DOMContentLoaded', function(e) {
            doc.body.style.fontSize = 12 + 'px';
        }, false);
    }
    

    refreshRem();

    flexible.dpr = win.dpr = dpr;
    flexible.refreshRem = refreshRem;
    flexible.rem2px = function(d) {
        var val = parseFloat(d) * this.rem;
        if (typeof d === 'string' && d.match(/rem$/)) {
            val += 'px';
        }
        return val;
    }
    flexible.px2rem = function(d) {
        var val = parseFloat(d) / this.rem;
        if (typeof d === 'string' && d.match(/px$/)) {
            val += 'rem';
        }
        return val;
    }

})(window, window['lib'] || (window['lib'] = {}));